The present invention pertains generally to electronic testing equipment and, more particularly, to electronic instruments for monitoring or measuring the performance of machinery such as internal combustion engines.
Precise ignition timing and idle adjustments are essential in order to achieve maximum fuel economy and performance in internal combustion engines. Because timing changes with engine RPM and load, it is important to be able to measure timing not only at initial or base timing, as is done with a conventional timing light, but also to be able to measure timing advance, which is possible with digital timing lights and advance timing lights. Most engines require that both initial and advance timing calibrations be set or checked at specific engine RPMs, or in some cases with a specific vacuum applied to the vacuum advance diaphragm on the distributor, or in some cases by the vehicle""s onboard computer. In the case of engines which are equipped with breaker point ignition systems, it will be necessary to set point dwell before adjusting timing.
Car manufacturers specify engine timing measured in degrees at certain engine speeds measured in RPM. Engine speed has to be maintained at a specified value for the timing reading to be valid. On a conventional digital timing light, the operator uses a switch to manually toggle a single display between the tachometer mode (reading engine RPM) and the timing mode (reading timing in degrees of advance).
Prior to beginning the timing check procedure, the stationary timing mark located on the engine must be found. On some engines, finding the timing mark is difficult or even impossible without a flashlight or some other source of light. Several timing light models available on the market have a small flashlight integrated into the case. The flashlight consists of an incandescent bulb, a lens, a bulb holder, an on/off switch, and some miscellaneous wires. The disadvantages of this design are that the light produced by the bulb is not very bright, the light bulb needs to be replaced periodically when it fails due to burning up or filament breakage due to a mechanical shock. Adding this feature also significantly increases the cost.
In the proposed design, the flash tube normally used to produce a strobe of light for engine timing measurements is also used to illuminate the engine compartment when looking for the timing marks. Depressing the flashlight button will interrupt the normal mode of operation and cause the flash tube to flash at a relatively high rate of approximately, for example, 25 Hz or higher regardless of the engine speed. At this high flashing rate, the human eye will perceive the light spot created by the flash tube and the lens in front of it as light essentially without flicker. When the flashlight button is released, the timing light switches back to normal mode of operation.
In a microcontroller or microprocessor controlled timing light, a flashlight on/off switch is required to add the flashlight feature of the invention. The software of a microcontroller or microprocessor controlled timing light generates a signal to trigger the flash tube at a relatively high rate to produce a light which is perceived by the human eye as continuous or constant. In other timing light designs, a flashlight on/off switch and a small circuit need to be added. This circuit will generate a square wave with a frequency of 25 Hz or higher to drive the flash-tube triggering circuit. The advantages of the new design are; brighter light (since the Xenon flash tubes produce brighter light than small incandescent bulbs); fewer parts, lower cost, and higher reliability since no additional parts are needed (light bulb, bulb holder, and lens, etc.).
A digital timing light with two displays simultaneously presenting engine speed and timing simplify the operation and allow to monitor engine speed constantly during the process of measuring the timing. This is especially useful for a one-person operation when a mechanic needs to manually operate the throttle with one hand to maintain proper engine speed, point the flashing light at the stationary and moving timing marks, operate the Increase and Decrease Advance switches, and read the displays. In accordance with several objects of the invention, there is provided a device for measuring and displaying information pertaining to the operation of a spark-ignited internal combustion engine, including a housing having a gripping portion and a pointing portion, a flash tube mounted within the pointing portion behind a lens at a distal end of the pointing portion, the flash tube electrically connected to a control circuit operative to sense electrical pulses from an engine and to control a triggering voltage supplied to the flash tube, a first display in the housing connected to the control circuit and operative to display a running speed of an engine, and a second display in the housing connected to the control circuit and operative to display an indication of timing of an engine.